It's amusing that the original (native) version ran smoothly on a 286 with EGA but this JS version gets the CPU running hard enough to turn on the fans on my 2014 MBP.

I would guess it's running at like a thousand FPS, could be wrong though.

Many of the normal rules aren't implemented (flips in the air, jumping off of rocks if you click at the right time, etc.).

It doesn't seem to have the Abominable Snow Monster (TM)

That looks like it's a recreation, though. Shouldn't it be possible to create an Emscripten port of the original? :)